Superheterodyne signaling system



Patented Oct. 22, 1929 ,UNITED STATES PATENT OFFICE ARTHUR EDWIN LEIGH SCANES, 0F STRATHFIELD, ENGLAND, ASSIGNOB TO ASSO- CIATED ELECTRICAL INDUSTRIES LIMITED, A. BRITISH COMPANY SUPERHETERODYNE SIGNALING- SYSTEM Application led May 4, 1925, Serial No. 27,629, and in England May 28, 1924.

My invention relates to radio-receiving systems, and particularly to superheterodyne systems.

One object of my invention is to provide a superheterodyne radio-receiving system in which the various triodes are caused to amlify the received signals several times at diferent frequencies.

Another object of my invention is to make more efficient utilization of the triodes of a radio-receiving system.

Another object of my invention is to provide a radio-receiving system having a plurality of triodes and coupling means associated therewith so that a triode detects a signal at one frequency and also amplilies the same signal at another frequency. f Another object of my invention is to pro` vide a radio-receving system in which the incoming signal is heterodyned a plurality of times and successive frequencies detected by certain triodes and amplified simultaneously by other triodes.

Another object of my invention is to provide a radio-receiving system containing a plurality of triodes which are simultaneously coupled by two or more resonant circuits tuned to different frequencies.

Another object of my invention is to pro vide a signal oscillation generator adapted to generate a fundamental oscillation frequency, and a plurality of harmonic frequencies, and means for simultaneously employing them for multiple heterodyning of an'incoming signal.

The reception of radio signals-is customarily accomplished by the interaction of tuned circuits and triode detectors. It is found advantageous, in certain systems, to employ a local oscillation generator, the output of which is combined with the incoming signal to produce beat phenomena which are then resolved to oscillations at a lower frequency and modulated in accordance with the incoming signal. Such a system is disclosed in the patent to Armstrong, No. 1,342,885. This system, as customarily employed, contains a'local oscillation generator, a detector triode for resolving the combined frequencies, a plurality of intermediate frequency amplifiers and a second detector.

his system, with a suitable number of amplifer tubes, may easil contain from six to ten vacuum tubes whic are expensive.

My invention provides means whereby a triode is caused to function as a beat resolver, taking the combined frequencies of a generator and an incoming signal and resolving them to a different frequency, and also operates simultaneously as an amplier at a frequency other than those involved in the preceding functions.

By this means, the number of triodes in the system is materially reduced, and much more efficient utilization is made of each triode.

Other objects and structural details of my invention will be apparent' from the following description, when read in connection with the accompanying drawing, wherein Fig. 1 is a diagrammatic view of a radio receiving system arranged according to a preferred embodiment of my invention, and

Fig. 2 is a diagrammatic View of an alternative circuit arrangement.

The circuits and apparatus of my invention are diagrammatically shown in the drawing in a fundamental form, consisting of a radio-receiving system containing three triodes coupled to a loop aerial. In the interest of simplicity, the complete cathode heating circuits are not shown.

The receiving system illustrated in Fig. 1

comprises an input circuit consisting of a frame aerial 1, an inductance 2 and a tuning condenser 3. High-frequency currents are induced in this circuit by an incoming signal. The local oscillator 4, tuned to a frequency, differing by the required value from the frequency of the received oscillations, is coupled to the inductance 2. The circuit 1, 2 and 3 is connected to the grid of a valve 5 through the condenser 6 and is connected, at its low potential end, through other apparatus hereinafter referred to, to the cathode of the valve 5. The normal grid potential of the valve 5 is determined by a high resistance 7 connected between its grid and cathode. The valve 5 detects or rectifies the received oscillation and oscillations duc to the local oscillator 4 to produce first beat oscillations in its anode circuit. The anode circuit may be supplied from a high voltage battery 8 through a choke coil 9. y

The oscillations at the first beat frequency are transferred to the grid of the second valve 10 by means of the condensers l1, 12, and a vtuned closed circuit comprising an inductance 13 and a condenser 14. The normal potential of the grid of the valve l0 is determined by a high resistance 15 connected between its grid and cathode. The first beat oscillations are amplified by the valve 10 and appear in thc anode circuit thereof which is fed from the high-voltage battery 8 through` the choke coil 16. These amplified oscillations are applied to the grid of a valve 17 through the condensers 18 and 19 by means of the closed circuit consisting of an inductance 20 and conf denser 21.

l A second local oscillator 22, arranged to generate oscillations differing in frequency rom that of the first beat oscillations by the 'required amount, is coupled to the inductancc 20 so that oscillatory potentials of the frequency of the oscillator 22 are applied to the grid of the valve 17. The normal potential of the grid of the valve 17 is determined yby a resistor 23 connected between the grid and the cathode thereof. The valve 17 recties the combined oscillations due to the local oscillator 22 and the first beat oscillation and second beat oscillation appear on the anode circuit which is fed from the high-tension battery through the choke coil 24.

The anode of the valve 17 is connected through a condenser 25 to a tuned closed circuit comprising an inductance 26 and a condenser 27. The lower end of this closed circuit is connected to the cathode. An inductance 28, tuned by a condenser 29 to the second beat frequency, is loosely coupled to the in- -ductance 26. The high-potentia'l end of the closed circuit thus formed is connected to the low-potential end of the frame aerial circuit 1, 2, 3 previously referred to, and the lowpotential end of the closed circuit 28, 29 is connected to the cathode of the valve 5 so that oscillations of the second beat frequency are applied to the grid of the valve 5. Alternatively,.the coil 28 may be aperiodic and closely coupled to the coil 26 and may be connected at its high-potential end to the grid of the valve 5 and at its low-potent-ial end to the cathode. In the latter arrangement, the coiI 28 serves also as a choke coil to prevent other high-frequency potentials leaking from the grid of the valve 5.

These oscillations reappear amplified in the anode circuit of the valve 5 and are applied to the grid of the valve 10 through the condensers 30, 31 by the aid of the tuned closed circuit 32, 33. A local oscillator 34, arranged to generate oscillations differing in frequency from the second beat oscillations lthe second beat oscillations and those due to the local oscillator 34 to form third beat oscillations in its anode circuit. The third beat oscillations are applied to the grid of the valve 17 through the coupling condensers 35 and 36 by means of the tuned closed circuit 37, 38 and are rectified by the valve 17.`

It will be evident that, if the originally received signal was modulated, modulation currents will be present in the anode circuit of thefvalve 17 In order to further amplify the modulation currents, the primary winding 39 of an audiofrequency transformer is connected in series with the choke coil 24 and the anode suppl circuit of the valve 17. The secondary wind ing 40 of this transformer is connected at its high-potential end through a choke coil 41 to the grid of the valve 5 and at its lowpotential end to the cathode so that modulation potentials are applied to the grid of the valve 5.

The purpose of the choke coil 41 is to prevent the leakage of high-frequency potentials from the grid of the valve 5. The modulation kpotentials applied to the grid of the valve 5 are amplified thereby and reappear in the anode circuit. In order to make the modulation apparent, a telephone is connected in series with the choke coil 9 in the anode supply circuit of the valve 5.

If preferred, the three local oscillators may be substituted by one local oscillator arranged to generate a fundamental frequency and several harmonic frequencies, as shown in Fig. 2, wherein the oscillation generators 22 and 34 are replaced by the inductors 52 and 51, these inductors being connected in shunt to the oscillation generator 4. The harmonic oscillations ma be made use of to provide the higher oscillation frequencies required. The fundamental or one of the lower harmonies may be used to provide the lowest oscillation frequency required.

It is apparent that the number of valves necessary for successive rectification is reduced bythe above-described high-frequency reflex operation. Although non-regenerative tubes are illustrated and described, it will be evident to those skilled in the art that the invention does notrequire that only non-re' los abled tomake more eiicient utilization of the triodes in a radio-receiving set.

While I have shown but two embodiments of my invention in the foregoing description, it is capable of other modifications therefrom, and it is desired, therefore, that only such limitations shall be placed thereon as are imposed by the prior art or indicated in the appended claims.

I claim as my invention:

1. In a radio-receiving apparatus, a plurality of vacuum tubes, a plurality of intertube coupling means tuned respectively to different frequencies and means including an oscillation generator and cooperating with said tubes and coupling means to produce from the received signal a plurality of different frequencies corresponding to said respective tunings.

2. In a radio-receiving apparatus, a plurality of vacuum tubes, a plurality of intertube coupling means each including a tuned circuit, a plurality of devices cooperating respectively with said tuned circuits and includinga source of energy of a frequency di'ering from that to which the corresponding tuned circuit is resonant for producing in the output of one of said tubes a still diderent frequency.

3. A radio-receiving apparatus, comprising a plurality of triode vacuum-tube devices, and a single local oscillation generator adapted to .generate oscillations at a fundamentalv frequency and at a plurality of harmonic frequencies, and means whereby said plurality of frequencies is caused to produce a plurality of successive changes in frequency whereby the received signal controls the ultimate frequency by the control of a series of intermediate frequencies.

4. A radio-receiving apparatus, comprising a plurality of triode vacuum-tube devices, and a single local oscillation generator adapted to generate oscillations at a fundamental frequency and at a plurality of harmonic frequencies, means including vacuum tubes whereby each frequency of said plurality of frequencies is caused to produce a beat-noteby combination with another frequency, the irst of said beat-notes being produced b such combination with the received signal requency and each vsuccessive beatnote being produced by such combination with the preceding beat-note and means whereby the output of a beat-note-producing means is amplified by the vacuum tube forming part of another beat-note-producin of the other of said devicesyaftuiied 'osciluntunedpaths comprising serially connected l capacitive reactors between the anode-of one of said devices and the grid of the other of said devices, a tuned oscillatory circuit connected across said pat-hs, and a tuned oscillatory circuit connected between said common cathode connection and the point on one of said pat-hs to which said first-mentioned oscillatory circuit is connected.

7 In apparatus for transferring etliciently electrical oscillatory energy of a plurality of frequencies from one electrical system to another, a plurality of tuned oscillatory systems interposed simultaneously between said systems, and a plurality of `untuned paths also interposed between said systems.

8. In apparatus for transferring efficiently high-frequency electrical oscillations at a plurality of frequencies from one electrical system to another, a plurality of oscillatory systems, each separately tuned to one of said frequencies, simultaneously interposed between said systems, and a plurality of untuned paths also interposed between said systems. y

9. In apparatus for amplifying electrical oscillatory energy at a plurality of frequencies, a plurality of electron-discharge devices, coupling means between certain of said devices comprising a plurality of oscillatory circuits, each of said circuits being tuned to one of said frequencies, and a plurality of untuned paths between said de.- vices.

10. A coupling network for high-frequency amplifiers comprising a plurality of tuned impedance devices serially connected, one of said devices having a plurality of untuned paths connected in shunt thereto, connections whereby intermediate points on said untuned paths may be connected ,to the anode of one thermionie device and the grid of a succeeding device, respectively, and a connection whereby another of said tuned impedance devices may be connected to the cathodes of said therrnionic devices.

l l1. The method of heterodyne reception'of a wide range of signal-modulated radio-carrier frequencies which comprises reducing in frequency any given one of said range of carrier frequencies in two or more detection stages, the beating frequencies for said stages beingsupplied from a local source of variable fundamental and harmonic frequencies, detecting the signal from the last resultant frequency of the series of'sta es, and repeating suc process of successive etection for any or all of other received frequencies within the range'of received frequencies, the beating-frequency from the local source, in each stage of detection, varying in the same ratio that the received frequency varies, the varying of the plurality of beating frequencies which act in the successive stages of detection being effected simultaneously by varying the fundamental frequency of the local source.

12. The method of heterodyne reception of a wide range of signal-modulated radio-carrier frequencies which comprises reducing in frequency any given one of said ran e of carrier frequencies in two or more etection stages, the beating frequencies for said stages being supplied from a local source of variable fundamental and harmonic frequencies, detecting the signal from the last resultant frequency of the series of stages, and repeating such process of successive detection for any lor all other received frequencies within the range of received frequencies, the beating fre uency from the local source, in each stage of etection, varying in the same ratio that the received frequency v varies, the varying ofthe plurality of beating frequencies which act in the successive stages of detection being effected simultaneously by varying the fundamental `frequency of the local source, the resultant frequencies, in the successive stages of detection,

also varying in the same ratio that the received frequency varies. f

13. The method of heterodyne reception of a Widerange of signal-modulated radio-carrier frequencies which comprises reducing in frequency any given one of said range of carrier requencies in two or more" detection stages, the beatin frequencies for said stages being supplied om anlocal source of variable harmonic frequencies, detecting the signal from the last resultant frequency of the series of stages, and repeating such process of successive detection for any or all other received frequencies within the range of received frequencies, the beating harmonic -frequency from the local source,i1n each stage of detection, varying in the same ratio that the received frequency varies, the varyin of the plurality of fbeating harmonics which act 'in the successive stages of detection being effected simultaneous y by varying the frequency of the local source.

14. The method of heterodyne reception of a -wide range of signal-modulated radio-carrier frequencies which comprises reducing in .frequency any given one of said range of carrier frequencles in two or more detection stages, the beating frequencies for said stages being supplied from a local source of variable harmonic frequencies, detecting the signal from the last resultant frequency of the series q of stages, and repeating such process of successive detection for any or all other received frequencies within the range of received frequencies, the beating harmonic frequency from the local source, in each stage of detection, varying in the same ratio that the received frequency varies, the varyin 'of the plurality of beating harmonics whic act in the successive stages of detection being effected simultaneously by varying the frequency of the local source, the resultant frequencies, in the successive stages of detection, also varying in the same ratio that the received frequency varies.

In testimony whereof, I have hereuto subscribed my name this 15th day of April, 1925.

ARTHUR EDWIN LEIGH SCANES.

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